Recent developments of the raven Corvus corax population in the Netherlands Recente ontwikkelingen van de raaf Corvus corax in Nederland
Renssen, T.A.; Vogel, R.L.
Limosa. september; 663: 107-116
1993
Document Number: 284573
The Raven became extinct in The Netherlands in the First half of this century, mainly as a result of human persecution. Regular breeding ended in most areas in the course of the 1920s. In 1966, a reintroduction project was started that appeared to be successful. Since 1976 the Raven has bred annually on the Veluwe, a large wood- and heathland area (1240 km-2). After a period of fluctuating low numbers, a marked increase took place from 1984 onwards (fig. 1, 2). In 1992, 50 breeding pairs and at least 31 territorial pairs were found, most of them on the Veluwe. Here, the species occurs in 65% of the 5 times 5 km squares. The spacing of territories is rather regular on the Veluwe, but highest densities occur in the central part of the area. Almost all breeding pairs are located in old pine forests Pinus sylvestris near heathland or drift sands. Since 1990 some pairs are breeding in fir-woods Pseudotsuga menziesii, damaged by gales. Breeding success is slightly lower than elsewhere in Europe, 2.1 young reared per breeding pair (calculated for pairs that started egg-laying only). It is expected that the Dutch breeding area will expand in the next decades, and that Dutch and German populations will interchange before the year 2000 (fig. 3). Territorial Ravens probably stay within their territories during the whole year. Non-breeders often birds occur in wandering groups. Non-breeding birds have been studied systematically since 1989. About 95% of all observations were made on the Veluwe (fig. 4). Since the winter of 1986/87 flocks of 30-50 non-breeding birds are found here each winter. Groups of 6-8 non-breeding birds are observed in the woodland area of the Utrechtse Heuvelrug (240 km-2) since spring 1992. Despite the strong increase, Ravens are seldom seen in agricultural areas. The size and dispersion of the flocks of non-breeding birds on the Veluwe probably depends on the abundance of food.